While various polyurethane soft foam materials are known for sound insulation, they are, unlike the foam according to the invention, not suitable for damping vibration. Thus DE-AS No. 19 23 161 and DE-OS No. 28 35 329 describe foam materials filled with minerals which, due to their great weight per unit volume of 0.5 to 1.25 kg/dm.sup.3, enable good sound insulation to be obtained. It is however not possible to damp the vibration of sheet metal with these materials as the loss factor of these foams is too small.
While it is true that DE-PS No. 27 56 622 is concerned with manufacturing foam materials with high loss factors, the process described, namely the impregnation of open-pored polyurethane or PVC foams with viscoelastic raw materials, e.g. polyolefins or organic resins or waxes containing inorganic filling materials, is very expensive.
DE-PS No. 33 13 624 is also concerned with the manufacture of a polyurethane soft foan with a high loss factor. However, the viscoelastic properties cannot be used as they are for damping vibration of sheet metal, such as e.g. bodywork floor assemblies and front walls in motor vehicles, because in order to damp vibration there has to be a coupling between the sheet whose vibration is to be damped and the viscoelastic material. This is not possible in the case of the known foam materials without using supplementary means. For this reason compact materials for damping vibration are today melted on to vehicle floor assemblies. This is a very expensive procedure. As the melting processes are generally carried out before or during painting of the bodywork, problems of paint soiling arise. Melting in separate ovens is associated with a great expenditure of energy, so that there is considerable interest in performing the vibration damping without separate melting processes.
An attempt has also been made (DE-OS No. 35 10 932) to use the viscoelastic properties of a foam material by applying adhesive coatings for coupling between sheet metal and foam, but the process involves additional expenditure.